The Cutting Edge of Medical Technology Content, Community & Collaboration
Crystalline silica is a common mineral found in the earth's crust. Materials like sand, stone, concrete, and mortar contain crystalline silica. It is also used to make products such as glass, pottery, ceramics, bricks, and artificial stone. Silica is a mineral made up of silicon and oxygen, two of the most common elements on the planet. It comes in several forms, although by far the most common is crystalline silica. Crystalline silica is so abundant that it makes up over 12% of the earth’s crust, making it the second-most common mineral on the planet.
Respirable crystalline silica means quartz and quartz is the most common of these, which transforms into cristobalite when heated at high temperatures (over 1450 °C). The presence of Cristobalite, and/or tridymite, which are contained in airborne particles, can be determined to be respirable size particles by performing a specific type of air sampling. The air sampling device used must be one specifically designed to meet the characteristics for respirable-particles, it must be size-selective and be one that is specified in the International Organization for Standardization (ISO) 7708:1995: Air Quality-Particle Size Fraction Definitions for Health-Related Sampling.
Respirable crystalline silica are very small particles that are at least 100 times smaller than ordinary sand you might find on beaches and playgrounds. It is created when cutting, sawing, grinding, drilling, and crushing stone, rock, concrete, brick, block, and mortar. Activities such as abrasive blasting with sand; sawing brick or concrete; sanding or drilling into concrete walls; grinding mortar; manufacturing brick, concrete blocks, stone countertops, or ceramic products; and cutting or crushing stone can result in unprotected workers being exposed to respirable crystalline silica dust. Industrial sand used in certain operations, such as foundry work and hydraulic fracturing (fracking), is also a source of respirable crystalline silica exposure. About 2.3 million people in the U.S. are exposed to silica at work.
Workers who inhale these very small crystalline silica particles are at increased risk of developing serious silica-related diseases, including:
To protect workers exposed to respirable crystalline silica, OSHA has issued two respirable crystalline silica standards: one for construction, and the other for general industry and maritime. The recently updated standard lowered the permissible exposure limit for the employee and provides the employer options in determining and developing the best control methods for their work sites.